Method and apparatus for detecting currency



1- 27, 1956 B. s. CAHILL 3,275,138

METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. 24, 1961 17 Sheets-Sheet 1 B. s. CAHILL 3,275,138

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METHOD AND APPARATUS FOR DETECTING CURRENCY Sept. 27, 1966 17 Sheets-Sheet 4.

Original Filed Jan. 424. 1961 METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. .24, 1961 B. S. CAHILL Sept. 27, 1966 17 Sheets-Sheet 5 p 27, 1966 B. s. CAHILL 3,275,138

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METHOD AND APPARATUS FOR DETECTING CURRENCY Sept. 27, 1966 17 Sheets-Sheet 7 Original Filed Jan. 24. 1961 Tb iiin METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. 24, 1961 B. S. CAHILL Sept. 27, 1966 17 Sheets-Sheet 8 B. s. CAHILL 3,275,138

METHOD AND APPARATUS FOR DETECTING CURRENCY Sept. 27, 1966 17 Sheets-Sheet 9 Original Filed Jan. .24. 1961 Se t. 27, 1966 B. s. CAHILL 3,275,133

METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. 24, 1961 17 Sheets-Sheet 1o METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. .24, 1961 B. S. CAHILL Sept. 27, 1966 17 Sheets-Sheet 11 Nhm METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. .24, 1961 B. S. CAHlLL Sept. 27, 1966 17 Sheets-Sheet l2 B. s. CAHlLL 3,275,138

METHOD AND APPARATUS FOR DETECTING CURRENCY Sept. 27, 1966 17 Sheets-Sheet 13 Original Filed Jan. .24, 1961 NQQ Sept. 27, 1966 a. s. CAHILL 3,275,138

METHOD AND APPARATUS FOR DETECTING CURRENCY Sid Sept. 27, 1966 B. s. CAHILL 3,275,138

METHOD AND APPARATUS FOR DETECTING CURRENCY Original Filed Jan. .24, 1961 17 Sheets-Sheet 16 METHOD AND APPARATUS FOR DETECTING- CURRENCY Original Filed Jan. 24. 1961 B. S. CAHILL Sept. 27, 1966 17 Sheets-Sheet l7 United States Patent 3,275,138 METHOD AND APPARATUS FOR DETECTING CURRENCY Bernard S. Cahill, Mount Prospect, 11]., assignor to National Rejectors, Inc., St. Louis, Mo., a corporation of Missouri Original application Jan. 24, 1961, Ser. No. 84,643, now Patent No. 3,180,491, dated Apr. 27, 1965. Divided and this application Aug. 2, 1963, Ser. No. 299,576

8 Claims. (Cl. 209--111.7)

This application is a division of Donald M. Danko et al. application Serial No. 84,643 for Currency Detectors which was filed January 24, 1961 and which issued April 27, 1965 as Letters Patent No. 3,180,491.

This invention relates to improvements in currency detectors. More particularly, this invention relates to improvements in methods and apparatus for identifying authentic paper currency.

It is therefore an object of the present invention to provide an improved method and apparatus for identifying authentic paper currency.

Each bill of the United States of America has one face thereof engraved with magnetic ink and has the other face thereof engraved with non-magnetic ink. As disclosed by the commonly assigned Smith et a1. application Serial No. 849,066, for Currency Detectors which was filed on October 27, 1959, and which has been abandoned, it is possible to move the magnetic face of an inserted bill past a magnetic head at a uniform rate of speed and thereby generate voltage variations which can be used to determine whether that bill is authentic or spurious. If no voltage variations are generated, the bill will be rejected. If the amplitudes of the voltage variations are too small, the bill will be rejected. If the amplitudes of the voltage variations are too large, the bill will be rejected. If too few voltage variations are generated, the bill will be rejected. Further, if the repetition rate of the voltage variations due to the inserted bill differs appreciably from the repetition rate of the voltage variations due to an authentic bill, the inserted bill will be rejected. As a result, currency detectors which move the magnetic face of a bill past a magnetic head at a uniform rate of speed, and thereby generate voltage variations which can be used to determine whether that bill is authentic or spurious, can effectively determine Whether an inserted bill is authentic or spurious.

In the said Smith et al. application, the magnetic head engages the bockground of the portrait of the inserted bill and coacts with the vertical lines of that background to generate the required voltage variations. Where the spacings of the vertical lines in the portrait backgrounds of bills differ materially, it is possible to use the voltage variations to differentiate between bills of different denominations as well as to differentiate between authentic and spurious bills. For example, the spacings of the vertical lines in the portrait backgrounds of one dollar bills differ materially from the spacings of the vertical lines in the portrait backgrounds of five dollar bills, and hence it is easy to use the voltage variations to differentiate between one dollar bills and five dollar bills. However, Where the spacings of the vertical lines in the portrait backgrounds of bills of different denomination do not difier materially, it is not practical to use the voltage variations to differentiate between those bills. Yet it would be desirable to be able to differentiate between bills of different denominations which have portrait backgrounds wherein the spacings of the vertical lines are similar. The present invention provides a currency detector that is able to difierentiate between bills of different denominations which have portrait backgrounds wherein the spacings of the vertical lines are similar; and it does so by providing a currency detector which optically senses disice tinctive portions of the inserted bill. The currency detector provided by the present invention will thus provide magnetic sensing plus optical sensing of inserted bills. It is therefore an object of the present invention to provide a currency detector which provides magnetic sensing plus optical sensing of inserted bills.

The currency detector provided by the present invention magnetically senses the magnetic face of an inserted bill and optically senses the non-magnetic face of that bill. As a result, for a bill to be accepted, each of the faces thereof must conform to the corresponding face of an authentic bill. As a result, if a spurious 'bill could be made so one face thereof closely simulated the corre-' of time which a bill requires to move past the magnetic sensing and the optical sensing systems. If the required signal is not received from the magnetic sensing system within that short period of time, and if the required signal is not received from the optical sensing system within that short period of time, the bill will be rejected. This is desirable because it reduces the likelihood that a spurious bill could, by moving past the magnetic sensing and the optical sensing systems and then back again, produce signals which would enable that bill to be accepted. Asa result, the currency detector provided by the present invention provides a high degree of protection against the acceptance of spurious bills. It is therefore an objectof the present invention to provide a currency detector, which accomplishes its magnetic sensing and its optical sensing Within a relatively short, predetermined period of time.

The non-magnetic faces of bills of the United States of America have alternating white and green areas, and the spacings of these areas are distinctively difierent on bills of different denominations. The currency detectorprovided by the present invention utilizes an optical sensing system that .can respond to those. distinctively different spacings to identify bills of a desired denomination. It is therefore an object of the present invention to provide a currency detector which utilizes an optical sensing system that can respond to the spacings between the alternating white and green areas on the non-magnetic faces of bills to identify and accept such bills.

The spacings of the vertical lines in the portrait backgrounds of two dollarbills are so similar to the spacings of the vertical lines in the portrait backgrounds of some other bills that it is not practical to use the vertical lines in the backgrounds of two dollar bills to generate voltage. variations that could differentiate two dollar bills from those other bills. Yet it would be desirable to provide a currency detector that could identify and accept two dollar bills. The present invention provides such a cur-. rency detector, and that currency detector magnetically senses the vertical lines in the portrait backgrounds of two dollar bills to obtain one accept signal and senses, the spacings between predetermined green areas on the non-magnetic faces of those bills to obtain a second accept signal; and when both accept signals are received it accepts thosebills. It is therefore an object of the present invention to provide a currency detector that magnetically senses the vertical lines in the portrait backgrounds of two dollar bills to obtain one accept signal and senses the spacings between predetermined green areas Patented Sept. 27, 1966 It is therefore an object on the non-magnetic faces of those bills' to obtain a.

second accept signal.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description, several preferred embodiments of the present invention are shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. 1 is a broken, plan view of one embodiment of bill-transporting device that is made in accordance with the principles and teachings of the present invention.

FIG. 2 is a broken, side eleva-tional view of the embodiment of bill-transporting device shown in FIG. 1,

FIG. 3 is a broken, sectional view through the embodiment of bill-transporting device shown in FIG. 1, and it is taken along the plane indicated by the line 3-3 in FIG. 1,

FIG. 4 is a sectional view of a few of the components of FIG. 3, it is taken along the plane indicated by the line 3-3 in FIG. 1, and it shows the shaft-carrying bracket of FIG. 3 in lowered position,

FIG. 5 is, a broken, sectional view through the embodiment of bill-transportingdevice shown in FIG. 1, and it is taken along the plane indicated by the line 5-5 in FIG. 1,

FIG. 6 is a sectional view, on a very large scale, through the embodiment of bill-transporting device shown in FIG, 1, and it is taken along the plane indicated by the line 6-6 in FIG. 5,

FIG. 7 is a side elevational view of the lower platen and associated parts used in the embodiment of billtransporting device shown in FIG. 1,

FIG. 8 is a bottom view of the platen and associated parts shown in FIG. 7,

FIG. 9 is a sectional view through the embodiment of bill-transporting device shown in FIG. 1, and it is taken along the plane indicated by the line 99 in FIG. 1,

FIG. 10 is a sectional view through the embodiment of bill-transporting device shown in FIG. 1, and it is taken along the broken plane indicated by the line 10-10 in FIG. 1,

FIG. 11 is a plan view, on an enlarged scale, through the bracket which holds the mounting for the magnetic head of the embodiment of bill-transporting device, shown in FIG. 1,

FIG. 12 is a sectional view, on a still larger scale, through the bracket of FIG. 11, and it is taken along the plane indicated by the line .12-12 in FIG. 11,

FIG. 13 is an elevational View of the rear plate of the embodiment of bill-transporting device shown in FIG. 1,

FIG. 14 is a sectional view, on a larger scale, through part of the embodiment of bill-transporting device shown in FIG. 1, and it is taken along the plane indicated by the line 14-14 in FIG. 1,

FIG. 15 is a sectional view, on the scale of FIG. 14, through another part of the embodiment of bill-transporting device shown in FIG. 1, and it is taken along the plane indicated by the line 15-15 in FIG. 1,

FIG. 16 is a side elevational view of a I-shaped bracket used in the embodiment of bill-transporting device shown in FIG. 1,

FIG. 17 is a partially-sectioned side view of the platens of the embodiment of bill-transporting device shownin FIG. 1 after those platenshave been rotated one hundred and eighty degrees about a vertical axis from the position shown by FIG. 2, and it shows the switches mounted on those platens,

FIG. 18 is a front elevational view of the front plate of the bill-transporting device of FIG. 1 as it appears when the bill-supporting platform is removed,

FIG. 19 is a schematic diagram of the power supply 21. used with the embodiment of FIG. 20 is a schematic diagram of the portion of the circuit of the embodiment of bill-transporting device of FIG. 1 which includes'the motor, the solenoids and the bill-operated switches,

FIG. 21 is a schematic diagram of the electronic. circuit for the magnetic sensing system used in the embodiment of bill-transporting device of FIG. 1,

FIG. 22 is a schematic diagram of the electronic circuit for the optical sensing system used in the embodiment of bill-transporting device of FIG. 1,

FIG. 23 is a schematic diagram of the portion of the circuit of the embodiment of bill-transporting device of FIG. 1 which includes the relays,

FIG. 24 shows the connections between the schematic diagrams of FIGS 19-23,

FIG. 25 shows the wave form that is generated by the light-sensitive element of FIG. 20 as the. leading portion of a two dollar bill passes that light-sensitive element,

FIG. 26 shows the Wave form at the output of an amplifier to which the wave form of FIG. 25 is supplied,

FIG. 27 shows the wave form at the output of the first section of the Schmitt trigger of FIG. 22,

FIG. 28 shows the wave form at the output of the secend section of that Schmitt trigger.

FIG. 29 shows the Wave form at the first grid of the pentagrid of a phantastron in the circuit of FIG. 22,

FIG. 30 shows the wave form at the second grid of the said pentagrid,

FIG. 31 shows the wave form at the cathode of the said pentagrid,

FIG. 32 shows the wave form at the plate of the said pentagrid,

FIG. 33 shows the wave form at the, output of the first stage of a gate amplifier,

FIG. 34 shows the wave form at the grid of the second stage of thatgate amplifier,

FIG. 35 shows the wave form at the output of said second stage of said gate amplifier,

FIG. 36 shows a composite wave format the input of the thyratron of FIG. 22,

FIG. 37 shows the wave form at the output of said thyratron,

FIG. 38 is a schematic diagram of another electron circuit for the optical sensing system used in the embodiment of bill-transporting device of FIG. 1, and

FIG. 39 is a schematic diagram of still another elec-.

tronic circuit for the optical sensing system used in the embodiment of bill-transporting device of FIG. 1.

Referring to the drawing in detail, the numeral 30 denotes a base for one embodiment of currency identification device that is made in accordance with the principles and teachings of the present invention. That base is generally rectangular in plan, and it has a stilfening flange that extends downwardly from the sides and ends thereof. That base has a largeopening 31therein, and that opening begins at a point about one third of the way toward the rear of that base, and that opening extends almost all the Way to the rear of that base.

The numeral 32 denotes a vertically-directed plate which has a horizontally-directed flange at the bottom thereof; and that flange serves as a foot. As indicated particularly by FIG. 2, the foot of the plate 32 is secured to the base 30 adjacent the front edge of that base. A plate 34 of U-shaped configuration is disposed above the plate 32, and that plate lies in the same plane as the lower plate 32. The closed end of the U-shaped plate 34 rests on the top of the plate. 32, and the arms of that plate project upwardly from the plate 32. A front plate 36 overlies the front face of the plate 34, and also projects downwardly beyond the bottom of that plate to overlie the front portion of the upper part of the plate 32. A horizontally-directed opening 38 is formed in the plate36, and that opening is wide enough to accommodate a two dollar bill when that bill is inserted lengthwise through that opening. Fasteners 40, shown in the form of machine screws, pass through openings adjacent the bottom of the front plate 36 and seat in threaded openings adjacent the upper end of the plate 32.

The numeral 42 denotes the rear plate for the embodiment of currency identification device shown by FIG. 1, and that plate has a horizontally-directed flange which acts as a foot. As indicated particularly by FIG. 2, the flange on the plate 42 is secured to the top of the base 30. The rear plate 42 is parallel to the plate 32, and it is in register with that plate. A U-shaped bracket 44 is suitably secured to the front face of the rear plate 42; and spot welds constitute a convenient way of securing that bracket to that plate. The upper right hand corner of the rear plate 42 is cut-away at 43, as shown particularly by FIG. 9.

The numeral 50 generally denotes a horizontallydirected platen which is disposed above and which is parallel to the base 30. That platen has a downwardlyextending wall portion 52 at the front thereof; and that wall portion has a vertical flange 54 at one side thereof, has a centrally-located rectangular opening 58 extending upwardly from the lower edge thereof, and has a vertical flange 62 at the other side thereof. The flanges 54 and 62 act to stiffen the wall portion 52. The platen 50 has a flange 64 which extends downwardly from one of the elongated sides thereof, and that flange is contiguous with the vertical flange 62 and extends almost all the way to the rear edge of that platen. An elongated opening 66 is formed in the platen 50, and that opening is parallel to the flange 46. An elongated slot 68 is formed in the platen 50, and that slot is formed at the longitudinallyextending center line of that platen. As indicated particularly by FIG. 8, the slot 68 is shorter than the opening 66. An opening 70 is provided in the platen 50 near the'front of that platen; and that opening is in register with the elongated slot 68. That opening is wider than the slot 68, and it is intermediate that slot and the wall portion'52. A second elongated opening 72 is provided in the platen 50; and that opening is parallel to, and has the same length as, the opening 66. The openings 66 and 72 are disposed on opposite sides of the elongated slot 68. A flange 74 is formed at the other elongated side of the platen 50, and that flange extends downwardly to the level of the bottom edge of the flange 64. That flange is contiguous with the vertical flange 54 of the vertical wall portion 52, and it extends almost all the way to the rear edge of the platen 50. The flanges 64 and 74 reinforce and stiffen the platen 50. A rectangular opening 76 is formed adjacent the rear edge of the platen 50, and that opening is intermediate the flange 64 and the elongated opening 66. A similar opening 78 is provided in the platen 50 adjacent the rear edge thereof, and that opening is intermediate the elongated opening 72 and the flange 74. The platen 50 terminates in a downwardlyinclined trailing edge 80. A notch 82 is formed in the trailing edge of the platen 50, and that notch extends inwardly beyond the downwardly-inclined trailing edge 80 of that platen. Similarly, a notch 84 is formed in the trailing edge of the platen 50, and that notch extends inwardly beyond the downwardly inclined trailing edge 80.

A vertical plate 46, which has a foot-like flange, is secured to the lower face of the platen 50 by that flange. Spot welds can be used to secure that foot-like flange to the lower face of that platen. In addition, the plate 46 has an ear 47, and that ear will be suitably secured to the platen 50. Similarly, a vertical plate 48, which has a footlike flange, is secured to the lower face of the platen 50 by that foot-like flange. In addition, the plate 48 has an car 49, and that ear is suitably secured to the platen 50. The ears 47 and 49 are spaced forwardly of the forward ends of the foot-like flanges on the plates 46 and 48,

respectively; and those ears rigidly secure the forward ends edges of the elongated openings 66 .and 72. The plates 46 and 48 are shorter than the elongated openings 66 and 72; and those plates terminate short of the notches 82 and 84, respectively.

A short vertical plate 75 has a foot 77; and that foot is secured to the platen 50 by a fastener, such as a machine screw. The plate 75 is alined with the vertical plate 48; but it is spaced a short distance rearwardly of the trailing edge of that plate. The plate 75 extends to the rear edge of the platen 50. A short vertical plate 79 has a foot 81; and that foot is secured to the platen 50 by a fastener, such as a machine screw. The plate 79 is alined with the vertical plate 46; but it is spaced a short distance rearwardly of the trailing edge of that plate. The plate 79 extends to the rear edge of the platen 50. The space defined by the confronting edges of the plates 48 and 75 is in register with the space defined by the confronting edges of the plates 46 and 79.

A securing flange 86 is provided at the front of the plate 46, and a securing flange 88 is provided at the front of the plate 48. As indicated particularly by FIG. 8, those securing flanges are suitably secured to the rear face of the vertical wall portion 52 of the platen 50. The vertical plates 75 and 79 are secured to the U-shaped bracket 44 on the rear plate 42, :as by fasteners 90; and since the plates 75 and 79 are fixedly secured'to the platen 50, the securement of those plates to the bracket 44 fixedly secures that platen 50 to the rear plate 42. The wall portion 52 at the front of the platen 50 is rigidly secured to the front plate 36 and to the U-shaped plate 34 by suitable fasteners.

The numeral 94 generally denotes a horizontal platen that is substantially identical to the horizontal platen 50. The platen 94 has a wall portion 96 at the front thereof; but instead of extending downwardly from the plane of that platen, that wall portion extends upwardly from that plane. The wall portion 96 has a vertical flange 98 at one side thereof, has a centrally-located rectangular opening 100 extending downwardly from the upper edge thereof, and has a vertical flange 102 at the other side thereof. The flanges 98 and 102 act to stifl'en the wall portion 96 of the platen 94. The platen '94 has a flange 104 which extends upwardly from one of the elongated sides thereof; and that flange is contiguous with the vertical flange 98. The flange 104 extends toward the rear of the platen 94, but it terminates at a point indicated by the numeral 105. An elongated opening 106, identical to the elongated opening 72, is formed in the platen 94; and that opening will be set in register with the elongated opening 66. An elongated slot 108, which is identical to the elongated slot 68 in the platen 50, will be set in register with that elongated slot. An opening is provided in the platen 94; and that opening is identical to, and will be set in register with, the opening. 70 in the platen 50. A second elongated opening 112 is formed in the platen 94, and that opening is identical to the opening 66; and that opening will be set in register with the opening 72 in the platen 50. A flange 114 is formed at the other elongated side of the platen 94, and that flange extends upwardly to the level of the upper edge of the flange 104. That flange is contiguous with the vertical flange 102 on the wall portion 96, and it extends almost all the way to the rear edge of the platen 94. The flanges 104 and 114 reinforce and stiffen the platen 94. ()penings 116 and 118 are provided in the platen 94 adjacent the rear thereof, and those openings are identical to the openings 76 and 78 in the platen -50. The opening 116 is in register with the opening 76 and the opening 118 is in register with the opening 78. The platen 94 is provided with an upwardly-inclined trailing edge 120; and notches 122 and 124 extend inwardly through that trailing edge and into the horizontally-directed portion of the platen 94.

The numeral 126 denotes a vertical plate which has a foot-like flange, and that flange is secured to the upper face of the platen 94. That plate also has an earand a 

6. APPARATUS FOR INDENTIFYING AND ACCEPTING AUTHENTIC CURRENCY COMPRISING BILL-GRIPPING MEMBERS THAT CAN GRIP A BILL, A LIGHT-SENSITIVE ELEMENT, SAID BILL-GRIPPING MEMBERS AND SAID LIGHT-SENSITIVE ELEMENT BEING MOVABLE RELATIVE TO EACH OTHER TO CAUSE RELATIVE MOVEMENT BETWEEN TWO DIFFERENTLY-COLORED PORTIONS OF A BILL AND SAID LIGHT-SENSITIVE ELEMENT, SAID LIGHT-SENSITIVE ELEMENT RECEIVING LIGHT FROM BOTH OF SAID DIFFERENTLY-COLOR PORTIONS OF SAID BILL DURING AT LEAST PART OF THE RELATIVE MOVEMENT OF SAID LIGHT-SENSITIVE ELEMENT AND SAID BILL-GRIPPING MEMBERS, A CIRCUIT RESPONSIVE TO CHANGES IN THE AMOUNT OF LIGHT RECEIVED BY SAID LIGHT-SENSITIVE ELEMENT, SAID CIRCUIT PROVIDING AN ACCEPT SIGNAL ONLY IF THE BILL IS AUTHENTIC AND OF PREDETERMINED DEMONINATION AND CAUSES LIGHT FROM BOTH OF SAID DIFFERENTLY-COLORED PORTIONS THEREOF TO REACH SAID LIGHT-SENSITIVE ELEMENT, SAID CIRCUIT NOT PROVIDING AN ACCEPT SIGNAL IF SAID BILL IS NOT AUTHENTIC OR IS NOT OF PREDETERMINED DEMONINATIONS OR DOES NOT CAUSE LIGHT FROM BOTH OF SAID DIFFERENTLY-COLORED PORTIONS THEREOF TO REACH SAID LIGHTSENSITIVE ELEMENT, AND A MEMBER THAT HAS A PORTION THEREOF WHICH DIRECTS A FINITE, PREDETERMINED, MINIMUM AMOUNT OF LIGHT ONTO SAID LIGHT-SENSITIVE ELEMENT WHENEVER A BILL IS NOT IN POSITION TO CAUSE LIGHT TO FALL ONTO SAID LIGHTSENSITIVE ELEMENT, SAID PORTION OF SAID MEMBER BEING MUCH SMALLER THAN SAID BILL AND AT LEAST ON OF SAID DIFFERENTLY-COLORED PORTIONS OF SAID BILL BEING SPACED INWARDLY OF THE EDGES OF SAID BILL SO SAID BILL COMPLETELY OVERLIES SAID PORTION OF SAID MEMBER, AND THUS SUBSTANTIALLY KEEPS SAID PORTION OF SAID MEMBER FROM DIRECTING LIGHT ONTO SAID LIGHT-SENSITIVE ELEMENT, FOR A PERIOD OF TIME COMMENCING PRIOR TO THE INSTANT THE INNERMOST OF SAID DIFFERENTLY-COLORED PORTIONS OF SAID BILL STARTS DIRECTING LIGHT ONTO SAID LIGHT-SENSITIVE ELEMENT AND CONCLUDES AFTER BOTH OF SAID DIFFERENTLY-COLORED PORTIONS OF SAID BILL HAVE DIRECTED LIGHT ONTO SAID LIGHT-SENSITIVE ELEMENT, SAID LIGHTDIRECTING MEMBER HAVING A LIGHT-DIRECTING VALUE WHICH IS CLOSE TO THE LIGHT-DIRECTING VALUE OF ONE OF SAID DIFFERENTLYCOLORED PORTIONS OF SAID BILL, WHEREBY THE VALUES OF LIGHT RECEIVED BY SAID LIGHT-SENSITIVE ELEMENT PRIOR TO, DURING AND AFTER SAID BILL CAUSES LIGHT TO FALL ONTO SAID LIGHT-SENSITIVE ELEMENT ARE WITHIN PREDETERMINED LIMITS, SAID LIGHTDIRECTING VALUE OF SAID LIGHT-DIRECTING MEMBER BEING SUFFICIENTLY DIFFERENT FROM THE AVERAGE OF THE LIGHT-DIRECTING VALUES, OF THOSE PORTIONS OF SAID BILL WHICH WILL DIRECT LIGHT ONTO SAID LIGHT-SENSITIVE ELEMENT, TO CAUSE SAID LIGHTSENSITIVE ELEMENT TO EXPERIENCE A CHANGE IN THE INTENSITY OF THE LIGHT THEREON WHENEVER A BILL CAUSES LIGHT TO REACH SAID LIGHT-SENSITIVE ELEMENT. 